Problem: How many cubic decimeters fit in $7$ cubic meters?
Answer: First we will figure out how many cubic decimeters fit in one cubic meter. There are $10$ decimeters in every meter. So a cubic meter is the same as a $ 10 \text{ dm} \times 10 \text{ dm} \times10 \text{ dm} $ cube. $1 \text{m} = 10 \text{dm}$ There are $10 \times 10 \times 10 = 1000 \text{ dm}^3 $ in each cubic meter, by the volume formula. Since we have $7$ cubic meters, and each cubic meter holds $1000$ cubic decimeters, we have a total of $7 \times 1000$ cubic decimeters. So $7000$ cubic decimeters fit in $7$ cubic meters.